Arabs make up 20 percent of the Israeli population and are generally exempted from military service while most Jewish citizens are drafted. A few Israeli Arabs volunteer for the army or paramilitary police, however.

Walla News said one of the Islamic State recruits previously served in Israel's Givati infantry brigade, a unit that has often operated in Gaza.

Walla did not name the man or provide details on when he left for Syria, saying only that he was a Muslim from a village in northern Israel, was estranged from his family and would have been discharged from the army in January 2014.

Asked about the report, an Israeli security official told Reuters: "We are familiar with this case." The official did not elaborate.

Security forces have been cracking down on suspected Islamic State sympathizers in its Arab communities and among Palestinians in the West Bank. The ultra-violent jihadi group also has a presence in the neighboring Gaza Strip and Egyptian Sinai.

Israeli concerns were raised in October after two videos surfaced in which militants identifying themselves as Islamic State members and speaking Arabic-accented Hebrew threatened to attack the country.